The present invention pertains to a hydraulic rotary damper, particularly adapted for a vehicle trailing arm suspension system, and wherein components of the damper are formed of composites including components formed of all reinforced plastic or components formed of metal which are overmolded with plastic materials at wear and seal surfaces.
Rotary dampers are typically used in automobile suspension systems, including trailing arm type suspensions, in particular, to damp the oscillatory motion of the suspension linkage. However, rotary dampers have rather lengthy seal lines or potential fluid leakage paths across the damper rotor between the fluid filled chambers of the damper. Accordingly, rotary dampers require relatively precise fits between parts and precise surface finishes of the respective parts to provide minimal fluid leakage and to avoid degraded damper performance. However, in mass produced automotive vehicle applications, for example, the manufacturing cost associated with forming the damper components of precision cast metal parts or machined metal parts is undesirable. It is to overcome the problems related to cost effective manufacture of rotary dampers which also provide required performance characteristics that the present invention is directed.
The present invention provides an improved rotary suspension damper for a vehicle suspension system.
In accordance with one aspect of the present invention, a rotary damper is provided which includes a rotor having a core portion constructed of powder metal and which includes a plastic overmolded layer on the hub and blades of the rotor, a housing constructed of reinforced plastic and molded over a metal valve ring assembly. Elastomeric seals are provided to retain a hydraulic damping fluid within the housing of the rotary damper. Internal fluid leakage between the rotor end faces and the side plates of the damper housing, as well as fluid leakage between the rotor tips and the body of the housing is controlled by dimensional clearances and by selecting a fluid with a viscosity to minimize fluid flow.
In accordance with another aspect of the invention, a rotary damper for a vehicle suspension system is provided with a rotor having a core portion of reinforced plastic formed over a metal hub, a body molded from reinforced plastic molded over a metal reinforcing ring assembly wherein the inner surface of the body and the outer surface of the rotor are both provided with plastic overmolded wear surfaces. The plastics used for the overmolded wear surfaces of the rotor and the body are preferably of different compositions and are different than the compositions of the core portions of the rotor and the body. Elastomeric seals retain the damping fluid within the device and ribs may be provided along the sides and end faces of the rotor and on inwardly extending projections of the body to control fluid leakage between rotor chambers.
In accordance with a further aspect of the invention, a rotary damper is provided for a vehicle suspension system wherein the rotor and body are each formed of long fiber reinforced plastics, the body is molded over a metal ring assembly and elastomeric seals provide sealing to contain fluid within the damper and to control fluid flow around the damper rotor.
The present invention further provides an improved rotary damper for a vehicle suspension system according to the above-mentioned improvements and which is further characterized by improved flow control valves for controlling the flow of hydraulic damping fluid in a way to allow the damper to react differently to torque caused when the vehicle wheel is raising (jounce) and when the wheel is lowering (rebound). The improved rotary damper may be tuned by selecting a proper valve seat, including selection of fluid passages in a valve seat plate and the configuration of valve disks so as to control flow through the valves.
Those skilled in the art will further appreciate the above-mentioned advantages and superior features of the invention together with other important aspects thereof upon reading the detailed description which follows in conjunction with the drawings.